Relativity in Transit July 2, 2006

One of the more interesting aspects of the theory of general relativity – and the interplay of gravity, space and time – that I think understand is the twins paradox. The venerable Stephen Hawkings describes it thus:

“Consider a pair of twins. Suppose that one twin goes to live on the top of a mountain while the other stays at sea level. The first twin would age faster than the second. Thus, if they met again, one would be older than the other. In this case, the difference in ages would be very small, but it would be much larger if one of the twins went for a long trip in a spaceship at nearly the speed of light. When he returned, he would be much younger than the one who stayed on earth.”

This can be taken to mean that international travel (by airplaine, of course) can actually serve the purpose of keeping us younger, however infinitesimal the effect may be. Think about it: if gravity has the ability to curve (read: slow down) space-time, the time we spend in the air “cheating” gravity allows time to speed by that much more quickly, albeit in millionths of a second, if not less.

So hypothetically, given the amount of time I’ve already spent flying from one place to another, particularly on the long-haul flights, I’m probably a handful of moments “younger” than other people who would otherwise be my age!

Or not. With the stress that accompanies international travel – and some trips are necessarily more stressful than others – I can’t help but feel all the worse for wear, and suspect others feel the same way.